WO2005045131A1

WO2005045131A1 - Coated paper as a printed material

Info

Publication number: WO2005045131A1
Application number: PCT/EP2004/007699
Authority: WO
Inventors: Franz Josef Becker; Viktor Uerlings
Original assignee: M-Real Oyj
Priority date: 2003-10-08
Filing date: 2004-07-13
Publication date: 2005-05-19
Also published as: JP4625008B2; US20070272382A1; BRPI0415178A; EP1670990A1; JP2007508462A; EP1522629A1; CN1863966A

Abstract

The invention relates to paper comprising: a) a paper substrate and b) a preparation completely covering at least one side of the paper substrate, said preparation containing at least one surfactant and at least one pigment having a particle diameter of 1 - 500 nm. The preparation contains binding agents, whereby the ratio thereof to the pigment is a maximum of 5 weight parts of binding agent: 100 weight parts of pigment (respectively in relation to the solid content). The invention also relates to a method for the production thereof.

Description

COATED PAPER AS PRINTING MATERIAL

The subject of the present application is a natural paper with good printability. Another object of the present application is to provide a process for producing natural papers having good printability.

In the paper industry, there is a constant desire to improve the printability of papers. This is especially true for papers used in offset printing, as well as papers for the new digital printing media, such as inkjet papers or papers for digital printing machines. The papers used for the printing processes mentioned can basically be divided into two classes of papers: natural papers and coated papers. In the coated papers, at least one coating is applied to the side of the paper to be printed, which usually consists of pigments, binders and additives. To improve the printability, it is also possible for a plurality of lines, such as two or three lines, to be applied to the coated papers. This improves the printability as a function of the coverage of the nonwoven fabric of the base paper, that is, the more coating is applied, the better the printability.

The applied coatings can be divided into two classes, namely the glossy and matte coatings. They differ in their composition and in the post-processing steps in the production of coated papers. Here, in particular, a calendering by means of a calender or a calender after application of the Beschhich- tion mentioned. The disadvantage here is that the appearance, ie the appearance as well as the feel, ie the feel of the paper, is influenced by the applied coatings. Natural papers do not have these disadvantages. Since they do not have a coating with the high coating weights of the coated papers, the original character of the paper is preserved. In particular, the rigidity and the surface structure of the natural paper are not or not significantly changed. This leads to a pleasant feeling when touching the papers (pleasant feel) and a pleasant look of these papers. For this reason, they are used for high quality applications such as office correspondence or sophisticated, especially artistically designed catalogs, brochures and books. However, the quality of printing on natural papers is worse than on coated papers. The surface contour of the natural paper can be seen in the print.

Due to the fiber structure of natural papers whose surface consists of mountains and valleys simplified, the printing ink is assumed to vary greatly in the printing process. This has a disadvantageous effect, especially in the case of multicolor printing, since superimposition of the individual printing inks occurs here, so that the surface structure of the natural paper becomes particularly visible in the print.

There has been no lack of attempts to combine both the visual appearance, as well as the feel of a natural paper with the good printability of a coated paper.

In EP 0 648 894 it is proposed to provide a board with a coating which has a coating weight of 1-5 g / qm and consists of a pigment having an oil absorption of at least 80 g / 100 g of pigment and a binder , A disadvantage is that the composition described in EP 0 648 894 can only be used on cardboard with a high weight, which preferably have a basis weight of at least 180 g / m.sup.2. In US 6,387,213, the printability of a paper by

Application of a composition comprising a hollow plastic component in a proportion of 30-60 wt .-% based on the dry weight of the coating. Further included in the formulation is a binder having a content of 40-70% by weight, based on dry weight, of the formulation which is a modified high molecular weight starch. The formulation should preferably be applied as a contour line on the paper substrate. The disadvantage here is the high cost of the coating, which are caused by the hollow body plastic pigment and the modified starch with high molecular weight.

In EP 1 146 171 another way to improve the printability of a paper will be described. On a paper substrate which has a surface roughness of less than 6 microns and a surface gloss of 5 - 80%, a Topstrich is applied, which contains a pigment and a rheology modifying / binder component. In this case, it is preferred that the top coat is applied as a single layer with a layer thickness which preferably corresponds to the size of a pigment particle. A disadvantage of the paper presented in EP 1 146 171 is that the paper substrate must have a defined surface roughness of less than 6 μm and that the top coat must be applied to the substrate with a layer thickness which corresponds to the size of the pigments.

In the post-published European patent application 03 000th

835.3 describes how a patterned paper can be made which is unevenly colored unevenly. A mixture containing at least one surfactant and at least one pigment is not uniformly applied to a paper, thus forming a latent image or pattern. In a subsequent step, the paper is dyed unevenly by applying a dye solution and subsequently dried. It is essential here that the mixture of surfactant and pigment is not uniformly applied to the paper, but is applied only at the places where later a pattern should be recognizable. The altered coloration can be both a more intense and a less intense color compared to the untreated area of the paper. European Patent Application 03 000 835.3 does not disclose that the mixture of surfactant and pigment is applied over its entire surface to a paper substrate.

The object of the present invention is to provide a

Paper that combines the good printability of coated papers with the feel and visual appearance of natural papers. In particular, the papers should be improved compared with the papers produced to date in such a way that very good printability can be achieved with a wide variety of printing methods, in particular with offset printing, digital printing and inkjet printing. Otherwise, the properties inherent in natural papers should be retained.

The technical problem of the present invention is solved by a paper comprising:

a) a paper substrate and

b) a preparation applied over at least one side of the paper substrate containing a surfactant and at least one pigment having a particle diameter of 1 to 500 nm, the preparation comprising binder in a ratio of pigment of not more than 5 parts by weight of binder: 100 parts by weight of pigment (in each case based on the solids content).

It has been found that the printability in the customary printing processes is improved if such a preparation penetrates into the paper substrate, at the same time retaining the feel and the visual appearance of the natural paper. The preparation completely or nearly completely encloses mainly the fibers located on the surface of the paper substrate. It is advantageous that the natural paper of the present invention can be made on aggregates that are common in the paper industry, so that no additional manufacturing aggregates are necessary. It is also advantageous that the natural paper of the present invention is recyclable, so that it can be pitched in conventional equipment, such as a pulper, and reused to recycle paper.

The term paper is to be understood in the context of this invention, the finished, printable paper. It can be available both as an endless product / roll product and as a format product. The paper comprises a paper substrate as carrier material and a preparation applied to at least one side of the paper substrate. The coating is a layer which is optionally applied to the side of the paper substrate on which the preparation is present. If coating weights are given, these refer to the mass applied per unit area after conditioning to constant weight

15 110 ° C (atro). Preferred embodiments will be discussed below.

The preparation can be applied in a preferred embodiment on both sides of the paper substrate, ie on the top and bottom of the paper substrate over the entire surface.

The preparation may be an anionic, cationic or neutral

Own 20 velvet charge.

In a preferred embodiment, the preparation per side has a coating weight of 0.5 - 20 g / qm (atro). Preferably, 1 to 15 g / m 2, more preferably 2 to 10 g / m 2, and particularly preferably 3 to 7 g / m 2 preparation are present on at least one side of the paper substrate.

In the preparation, 0.05 to 2.5 g / m 2 (atro) surfactant are preferably present per side. A preferred embodiment comprises 0.1-2.0 g / m 2, Preferably, 0.2-1.5 g / m2 and most preferably 0.3-0.7 g / m2 surfactant in the preparation.

The surfactant may preferably be an anionic, cationic, nonionic or amphoteric surfactant.

Suitable surfactants may for example be selected from (1) hydrophilic polydialkylsiloxanes, (2) polyalkylene glycol, (3) polypropylene oxide-polyethylene oxide copolymers, (4) fatty acid ester-modified compounds of phosphate, sorbitan, glycerol, polyethylene glycol, sulfosuccinic acids, sulfonic acid or Alkylamine, (5) polyoxyalkylene-modified compounds of sorbitan esters, fatty amines, alkanolamides, castor oil, fatty acid, fatty alcohol, (6) quaternary alcohol sulfate compounds, (7) fatty imidazolines, (8) polyether-modified trisiloxanes, and (9) Mixtures thereof.

Specific examples of water- or alcohol-soluble surfactants from the abovementioned classes of substances are, for example, (1) poly (oxyalkylene) modifications of (a) sorbitan esters (eg Alkamuls PSML-4 (poly (oxyethylene) sorbitan monolaurate), Alkamuls PSMO-20 (Poly-

(oxyethylene) sorbitan monooleate), Alkamuls PSTO-20 (poly (oxyethylene) sorbitan trioleate), Alkaril Chemicals); (b) fatty amines (eg Alkaminox T-2, T-5 (tallow aminoethylate), Alkaminox SO-5 (soya amine oxyethylate), Alkaril Chemicals), (Icomeen T-2, Icomeen T-15, ICI Chemicals); (c) castor oil (eg, Alkasurf CO-10, Alkasurf CO-25B (castor oil oxyethylate), Alkaril Chemicals); (d) alkanolamide (eg, alkamides C-2, C-5 (coconut oil alkanolamide oxethylate), Alkaril Chemicals); (e) fatty acids (eg Alkasurf 075-9, Alkasurf 0-10, Alkasurf 0-14 (oleic acid oxyethylates), Alkasurf L-14 (lauric acid oxyethylates), Alkasurf P-7 (palmitic acid oxyethylates) Alkaril Chemicals); (f) fatty acid alcohol (eg Alkasurf LAN-1, LAN-3, Alksasurf TDA-6, Alkasurf SA-2, (linear alcohol ethoxylates), Alkasurf NP-1, NP-11, Rexol 130 (nonylphenoloxyethylate), Alkasurf OP- 1, OP-12 (octylphenoloxyethylate), Alkasurf LA-EP-15, Alkasurf LA-EP-25, Alkasurf LA-EP-65 (linear alcoholoxyalkylates)); (2) hydrophilic poly (dimethylsiloxanes) such as (a) having a monocarbinol end group provided poly (dimethlysiloxane) (PS558, Petrarch Systems Inc.) and dicarboxylated poly (dimethylsiloxane) (PS555, PS556, Petrarch Systems Inc.); (b) Poly (dimethylsiloxane) -b-poly (methylsiloxane-alkylene oxide) copolymers (PS 073, PS 072, PS 071, Petrarch Systems Inc.), Alkasil HEP 182-280, Alkasil HEP

5 148-330 (Alkaril Chemicals), non-hydrolysable copolymers containing Si-C bonds; (c) poly (dimethylsiloxane) -b-poly (propylene oxide) -b-poly (ethylene oxide) copolymers (Alkasil NEP 73-70, Alkaril Chemicals) a hydrolyzable copolymer containing Si-O-C bonds; (d) polyquaternary poly (dimethylsiloxane) copolymers (which can be obtained by the addition reaction of an α, ω-hydrogenpolysiloxane with olefinic bond-containing epoxides and then reacting the product with a diamine); (3) fatty imidazolines and their derivatives such as (a) alkazine-O (oleyl derivative); (b) Alkazine TO (tall oil derivative); (c) Alkateric 2C1 B (dicarboxylic acid cocoimidazoline sodium salt) Alkaril Chemicals; (d) Arzoline-4; (e) Arzoline-215, Baker Chemicals; (4) fatty acid esters of (a) 5 phosphates (eg, Alkaphos B6-56A, Alkaril Chemicals); (b) sorbitan (eg, Alkamuls STO (sorbitan trioleate), Alkamuls SML (sorbitan monolaurate), Alkamuls SMO (sorbitan monooleate), Alkaril Chemicals); (c) glycerol compounds (eg Alkamuls GMO-45LG (glyceryl monooleate), Alkamuls GDO (glyceryl dioleate), Alkamuls GTO (glyceryl trioleate); (d) poly (ethylene glycols) (Alkamuls 600 DO (dioleate), Alkamulso 400-ML (monolaurate), Alkamuls 600MM (monooleate), Alkamuls 600 DL (dilaurate), Alkamuls 600 DT (Ditalg), Alkaril Chemicals), (e) sulfosuccinic acid (eg, Alkasurf SS-O-75 (sodium dioctyl sulfosuccinate), Alkasurf SS-DA4-HE (oxyethylated Alcohol sulfosuccinate), Alkasurf SS-L7DE (sodium sulfosuccinate ester of lauric diethanolamide), Alkasurf SS-L-HE (sodium lauryl sulfosuccinate), Alkaril Chemicals), 5 (f) sulfonic acid (eg, Alkasurf CA (calcium dodecyl benzene sulfonate), Alkasurf IPAM (isopropylamine dodecyl benzene sulfonate), Alkaril Chemicals (g) Alkylamines (eg, alkamides SDO (soy diethanolamide), alkamides CDE (coconut diethanolamide), alkamides 2104 (coconut fatty acid diethanolamide), alkamides CMA (coco monoethanolamide), alkamides L9DE (lauryl diethanolamide), alkamides L7Me (lauryl mono-O ethanolamide) , Alkamides L1 PA (lauryl monoisopropylamide), Alkaril Chemicals); (5) quaternary compounds such as (a) non-polymeric quaternary ammonium ethosulfate (eg, Finquat CT, Cordex T-172, Finetex Corporation); (b) quaternary dialkyl dimethyl methosulfate (eg, Alkaquat DHTS (hydrogenated tallow)); (c) alkoxylated quaternary difatty methosulfate (eg Alkasurf DAET (tallow derivative)); (d) quaternary fatty imidazoline methosulfate (eg, alkaquat T (tallow derivatives), Alkaril Chemicals); (6) water soluble copolymers of lipophilic poly (propylene oxide) with hydrophilic poly (ethylene oxide) such as (a) methanol soluble Tetronic 150R1, Pluronic L-101, Tetronic 902, Tetronic 25R2 (BASF Corporation), Alkatronic EGE-1 (Alkaril Chemicals); (b) water-soluble Tetronic 908, 50R8, 25R8, 904, 90R4, Pluronic F-77, all from BASF Corporation, and Alkatronic EGE 25-2 and PGP 33-8 from Alkaril Chemicals; (7) poly (alkylene glycol) and its derivatives such as (a) polypropylene glycol (Alkapol PPG 425, Alkapol PPG-4000, Alkaril Chemicals); (b) poly (propylene glycol dimethacrylate), poly (ethylene glycol diacrylate), poly (ethylene glycol dimethacrylate), poly (ethylene glycol monomethyl ether), poly (ethylene glycol dimethyl ether), poly (ethylene glycol diglycidyl ether) (all from Polysciences); (c) poly (1,4-oxybutylene glycol) (Scientific Polymer Products) and the like.

Preferred surfactants include linear alcoholoxyethylates (e.g.

Alkasurf LA-EP-65, LA-EP-25 and LA-EP-15), nylphenoloxyethylates (eg Alkasurf NP-11 available from Alkaril Chemicals and Rexol 130 available from Hart Chemicals), octylphenoloxyethylates (eg from Alkaril Alkasurf OP-12 available from Chemicals), oleic oxyethylates (eg, Alkasurf 0-14 available from Alkaril Chemicals), poly (dimethylsiloxane) -b-poly (propylene oxide) -b-poly (ethylene oxide) copolymers (eg, Alkasil NEP 73 available from Alkaril Chemicals -70), castor oil oxyethylates (eg, Alkasurf C025B available from Alkaril Chemicals), cocoimidazole dicarboxylic acid sodium salts (eg, Alkateric 2C1B available from Alkaril Chemicals) and coconut fatty acid diethanolamide (eg, Alkamide S104 available from Alkaril Chemicals). The Alkasurf surfactants are advantageously biodegradable.

[0024] Further preferred surfactants are ethylene oxide / propylene oxide modified fatty alcohols, and modified fatty alcohol polyglycol ethers, such as the Hydropalat ^® XP 120 (available from Cognis / Henkel) In the preparation, preferably 0.1 to 19.5 g / m 2 (atro) pigment are present. Preferably, in the preparation, 0.2 to 19.3 g / m 2, more preferably 0.3 to 18.5 g / m 2, more preferably 0.4 to 18 g / m 2, and most preferably 0.45 to 17.5 g / qm pigment before. The pigment may preferably have a cationic and / or anionic and / or nonionic total charge. For the purposes of this invention, anionic pigments are those pigments in which the surface of the pigment has an overall anionic charge. Cationic pigments are those pigments in which the surface of the pigment has a total cationic charge. Nonionic pigments are those pigments in which the surface of the pigments has a neutral or substantially neutral total charge.

The pigment is preferably an oxide and / or a mixed oxide of a metal. But it can also be the oxide and / or mixed oxide of a semi-metal / Halbeiters.

The pigments used in the preparation preferably have a large specific BET surface area of preferably 50 to 800 m ² / g and more preferably from 100 to 400 m ² / g. The pigment particles themselves have a diameter of 1-500 nm, preferably 10-100 nm and more preferably 20-70 nm.

The pigments may preferably be selected from

Group consisting of oxides of metals or semi-metals, such as silicon, magnesium, calcium, aluminum, zinc, chromium, iron, copper, tin or lead. Preferred pigments are silicic acids, gibbsite, bayerite, northeast rimite, boehmite, pseudoboehmite, diaspore, aluminum oxides, preferably aluminum oxide, aluminum hydride, magnesium silicate, basic magnesium carbonate, titanium dioxide, tin oxide, aluminum silicate, calcium carbonate, talc, clay, hydrotalcite, silicon dioxide, colloidal silicon dioxide, precipitated silica, inorganic substances such as diatomite, organic substances such as resinous pigments from melamine-formaldehyde resins, urea-formaldehyde resins, ethylene resins, styrene resins, acrylate resins, or combinations thereof.

Colloidal suspensions of Si0 ₂ -

Particles, which are preferably non-porous SiO ₂ particles are used. The suspension may have an anionic or cationic charge. The particle size of the Si0 ₂ particles may in this case vary from 1 to 100 nm, the particle size preferably being from 10 to 50 nm. As an example of the pigments include the Cartacoat ^® K grades from. Clariant for this class, in particular the Cartacoat ^® 301A liquid, the liquid Cartacoat ^® 302A, the Cartacoat ^® 302C liquid and Cartacoat ^® 303A liquid. Alternatively, anionic or cationic colloidal silica can be used, which is sold under the trade name Ludox ^® CL or Ludox ^® TMA from Grace-Davison.

The preparation may preferably contain at least one additive. Additives which can be used are those which are familiar to the person skilled in the art, for example rheology modifiers, viscosity regulators (thickeners), dyes or brighteners. If a viscosity regulator is used, it is preferred that cross-linked, modified polyacrylates are used, such as the Cartacoat ^® MS liquid, available from the Fa. Clariant. According to the invention, however, the preparation contains a maximum binder in a ratio of binder to pigment (in each case based on solids content) of 5: 100, preferably 3: 100, more preferably at most 2: 100 to obtain the feel of natural paper.

The binders used are preferably those which do not crosslink, so that no solidification of the applied preparation layer takes place. Strictly speaking, according to the invention, no "binder" is used in the preparation, but rather thickeners or viscosity regulators are used to adjust the flowability of the preparation, but they can also be used as binders in papermaking, for example cellulose (US Pat. such as carboxymethylcellulose (CMC) .The thickeners are used in such small amounts that they are not used in the preparation as binders. act demittel, so do not bind the pigments to each other and / or the pigments to the paper substrate, but only adjust the viscosity and flowability of the applied preparation to a desired value. Such thickeners or viscosity regulators are well known to those skilled in the papermaking art. At the thickener according to the invention no special claim is made. The amount of thickener used is within the usual range in which such agents are used and depends on the properties of the thickener used.

Binders for the purpose of binding the pigments to one another and to the paper substrate is not used according to the invention in the preparation. Even if a thickener which is also suitable as a binder is used, it is present only in amounts which do not allow binding as described above. Such a preparation without a "binder" used for the purpose of binding improves the printability of the paper substrate, without substantially changing the haptic, so that it substantially corresponds to that of natural paper.

The paper substrate preferably contains a filler. It is preferred that the filler has a void volume. The void volume of the filler may preferably be measured by the oil number of the filler according to DIN EN ISO 787-5.

Preferably, the filler according to DIN EN ISO 787-5 an oil number of 10 - 150 g / 100g filler, more preferably from 30 - 80 g / 100g filler and more preferably from 30 - 70 g / 100g filler.

The filler may preferably be selected from the group consisting of chalk, precipitated chalk, clay, talc, clotted clay, alumina, aluminum hydroxide, gypsum, alumina hydrate, silica, silicic acid, diatomaceous earth, titanium dioxide and mixtures thereof. The filler may further preferably have an anionic or a cationic total charge. The content of filler in the paper substrate is preferably 3 to 30

Wt .-%, based on the total weight of the paper substrate after conditioning to constant weight at 110 ° C (atro). The proportion of filler is preferably 5-25% by weight, more preferably 7-20% by weight, particularly preferably 9-18% by weight and most preferably 10-15% by weight.

The paper substrate may preferably contain at least one additive. Preferred additives are wet strength agents, starches, defoamers, retention aids, brighteners, dyes and mixtures thereof. In a preferred embodiment, a proportion of wet strength agent is present in the paper substrate, which enables the paper substrate to be moistened again in the subsequent processing steps without the strength being reduced to such an extent by water absorption that the paper web breaks off during subsequent processing steps.

The paper substrate may contain any of the fibers commonly used in the art, e.g. Pulp or groundwood. Preferably, the paper substrate contains a mixture of long fiber and short fiber pulps.

The paper preferably has a basis weight measured according to

ISO 536 from 40 to 400 gsm. Preferably, the basis weight is 60 to 300 gsm, more preferably 70 to 280 gsm, and most preferably 80 to 250 gsm.

The preparation can be applied to at least one side of the paper substrate online, ie within the paper machine on the paper substrate. Preferred application aggregates are the size press, the size press application units, the film press, the billblade, the curtain coater, the air brush, the blade, the doctor blade application and the spray coating.

However, it is also possible, the preparation in one of the preparation of the paper substrate subsequent finishing step, at least the to apply one side of the paper substrate. This can be done with application units which are familiar to the person skilled in the art, for example with a size press, a size press similar to a size press, a film press, a blade, an air brush, a squeegee, a curtain coater, a spray coater or a reverse coater. gravure coating unit.

Unexpectedly, the preparation improves the printability of the paper substrate, without significantly or adversely affecting the optical or haptic properties of the paper substrate. The paper substrate retains or retains almost the visual and haptic impression of a non-treated natural paper. The preparation penetrates the entire surface and evenly into the surface of the paper substrate and unexpectedly prevents the otherwise caused by the mountains and valleys of the paper surface irregularity of a subsequently applied pressure. For example, in offset printing, the color is uniform. An indication of this is the so-called print image (mottling) of the printed paper. The print image speed indicates how homogeneous the printout is in offset printing on the paper. With a paper of the present invention, the homogeneity of offset printing is comparable to the homogeneity of offset printing on a coated paper. Furthermore, the paper of the present invention has a stiffness and volume comparable to untreated and uncoated papers.

In a further embodiment, on the same side of the

Paper substrate on which the preparation is applied, be present on the preparation at least one further coating.

The coating preferably contains at least one pigment and at least one binder.

In a preferred embodiment, the applied pigment has a particle diameter of 1 to 500 nm and may preferably be selected are selected from the group consisting of oxide and / or mixed oxide of a metal, oxide and / or mixed oxide of a semi-metal / semiconductor and mixtures thereof. More preferably, all pigments can be used, which can also be used in the preparation as a pigment.

The coating may preferably contain at least one further additive. Additives which can be used are all additives which are familiar to the person skilled in the art, for example binders, viscosity regulators (thickeners), brighteners, defoamers, dyes, dispersants and surfactants. Surfactants which can be used are all surfactants which are familiar to the person skilled in the art and preferably the surfactants used in the preparation. Furthermore, all viscosity regulators can be used, which can also be used in the preparation. The coating preferably has an application weight of 0.5 to 20 g / m 2 (atro) per side. Preferably, the coating weight of the coating is 2-15 g / m2, more preferably 3-12 g / m2, and most preferably 3-10 g / m2. The coating weight of the coating is preferably such that the surface of the paper substrate on which the preparation is homogeneously wetted by the coating.

The coating can be applied on both sides of the paper substrate, if a preparation is present on both sides of the paper substrate. However, it is also possible that if a preparation is present on both sides of the paper substrate, the coating is applied only on one side of the paper substrate on the preparation.

The coating may be anionic, cationic or neutral

Have total charge. Preferably, the coating has a total anionic charge if the preparation has a total cationic charge, or the coating preferably has a total cationic charge if the preparation has a total anionic charge. The coating can be applied with any application unit that is familiar to the expert. Furthermore, the coating can be applied inside the paper machine (online), ie during the production of the paper substrate. However, it is equally possible for the coating to be applied after production of the paper substrate in a subsequent processing step. Suitable application units include, for example, the size press, the size press application units, the film press, the blower coater, the air brush, the squeegee, the curtain coater and the spray coater.

All the above papers (with or without the coating) may be subjected to further post-treatment steps. So the surface of the paper can be further smoothed. This can be done by a calender, a matt calender, a calender or a brush calender. Advantageous are those methods in which the smoothness of the paper is increased without significantly reducing the volume of the paper by this step. Alternatively, the surface contour of the paper can be changed by an embossing step. For this purpose, e.g. a stamping calender suitable. The surface contour can be changed on both sides of the paper or only on one side of the paper, which is preferably the side on which the preparation is present.

All of the abovementioned papers can be used as printing material in printing processes which are familiar to the person skilled in the art. It is preferable that the printing method is selected from the printing methods consisting of offset printing, digital printing, inkjet printing, gravure printing, flexographic printing, newspaper printing, letterpress printing, sublimation printing, laser printing, electrophotographic printing and combinations of the aforementioned printing methods.

By applying the coating on the side of the paper substrate on which the preparation is present, the printability of the paper is further improved. Unexpectedly, however, the coating does not or does not substantially change the character of the paper. Both the appearance and the feel of the paper are not affected by the coating or not significantly adversely affected. The paper retains the character of an uncoated paper. Compared to untreated papers, however, the print quality is significantly improved.

The present invention will be illustrated by the following examples without being limited thereto.

Examples

1. Preparations

1.1. Preparation of Preparations 1 to 3

In the shown in Table 1 amount of water of the desired viscosity Tylose ^® H60000 YP2 is dissolved with stirring for adjustment. After a clear solution, the Hydropalat 120 ^® EXP is added. Then add the appropriate pigment slurry. It is stirred for 30 minutes to get the preparations 1-3.

Table 1

1) Tylose ^® H60000 YP2: carboxymethylcellulose with a molecular weight of 60,000 u (Clariant) 2) Hydropalat ^® 120 EXP: nonionic surfactant based on EO / PO modified fatty alcohol, modified fatty alcohol polyglycol ether (Cognis / Henkel) 3) Ludox ^® CL: cationic colloidal suspension of silica in water (30% by weight of Si0 ₂ content; Grace Davison) 4) Cartacoat ^® K 301A liquid: colloidal suspension of non-porous Si0 ₂ particles (pH 10, 30% Si0 _2, particle size 12 nm, Clariant ) 5) Ludox ^® TMA: anionic colloidal silica in water (34% by weight of Si0 ₂ content; Grace Davison)

1.2. Application of Preparations 1 to 3 on a paper substrate

A neutral sized paper with a basis weight of 120 g / m ² (filler content 15%, filled with PRECARB 200 (Schäfer lime), precipitated calcium

5 C0 ₃ , oil number (measured according to DIN EN ISO 787-5) 65g / 100g powder) is immersed in one of the preparations 1 to 3. Excessive amount of preparation is squeezed between two rubber rollers and the paper is then dried with a photo-dryer (heated metal roller around which a textile web passes, the paper is brought into the nip between metal roller and textile web for drying). The coating weight of the preparation on the paper substrate is 3 g / m ² (atro) per side.

1.3. Evaluation of printability 5 The paper substrates provided with Preparations 1 to 3 and, for comparison, the untreated paper substrate and a commercial coated paper (150 g / m ² total weight, satin finished, 20 g / m ^{2 of} a pigment coating are applied on each side of the paper). , are printed on one side with a Prüfbau device with a blue ink. Subsequently, the homogeneity and intensity of the printed blue area is visually assessed, the grade 1 indicating a very good homogeneity and intensity of the printed blue area, and the grade 6 indicating an insufficient homogeneity and intensity of the printed blue area. The assessment is shown in Table 2

Table 2

The commercial, coated paper shows a very good printability with the grade 1, while the paper substrate has only insufficient printability (grade 6). Unexpectedly, on the other hand, the paper substrate, when provided with one of the preparations 1 to 3, has printability which is only marginally worse with the 1-2 mark than the printability of the coated paper. Nevertheless, the haptic, as well as the visual appearance of the provided with the preparations paper substrates is not or not significantly changed.

2. Coatings

2.1. Preparation of Coatings 1 to 4

The indicated in Table 3, the amount of water Acronal 500D ^® and Mowiol ^® 8/88 solution was added with stirring. Are then added to the corresponding pigment slurry, and in the case of the coating 1 in addition, the Cartacoat ^® MS fl., Too. It is stirred for 30 minutes to obtain the coatings 1 to 4. Table 3

6) Cartacoat ^® 302C: cationic colloidal suspension of non-porous Si0 ₂ particles (pH 4, 30% Si0 _2, particle size 25 nm, Clariant) 7) Cartacoat ^® 303A: colloidal suspension of non-porous Si0 ₂ particles (pH 9, 30% Si0 _2, particle size 50 nm, Clariant) 8) Cartacoat ^® MS fl: crosslinked modified polyacrylate (37% solids) 9) Acronal 500D ^®: aqueous dispersion of a polystyrene-vinyl acetate copolymer (50 wt .-%, BASF AG) 10) Mowiol ^® 8/88-solution: 15% polyvinyl alcohol solution, 15% solution of Mowiol 8/88 ^® (Clariant) in water

2.2. Application of the coatings 1 to 4 on a paper substrate, which was treated with one of the preparations 1-3

A paper substrate provided with one of the preparations 1 to 3 according to 1.2 is immersed in one of the coatings 1 to 4. Excess amount of coating is squeezed between two rubber rollers and the paper is closing with a photographic dryer (heated metal roller, around which a textile web runs, the paper is introduced into the gap between metal roller and textile web for drying) dried. The coating weight of the coating on the paper substrate provided with the preparation is 3 g / m ² (atro) per side.

2.3. Assessment of printability

The paper substrates provided with the coatings 1 to 4 and, for comparison, the untreated paper substrate, as well as a commercially available coated paper (150 g / m ² total weight, satined, 20 g / m ^{2 of} a pigment coating are applied to each side of the paper) are provided with a Prüfbau device printed with a blue ink on one side. Subsequently, the homogeneity and intensity of the printed blue area is visually assessed, the grade 1 indicating a very good homogeneity and intensity of the printed blue area, and the grade 6 indicating an insufficient homogeneity and intensity of the printed blue area. The assessment is shown in Table 4.

Table 4

The commercial, coated paper shows a very good printability with the grade 1, while the paper substrate has only insufficient printability (grade 5). Unexpectedly, on the other hand, the paper substrate, when provided with one of the preparations 1 to 3 and subsequently with one of the coatings 1 to 4, exhibits a printability comparable to grade 1 with the printability of the coated paper. Nevertheless, the haptics and the visual appearance of the paper substrates provided with the preparations and coatings are not or not significantly changed.

Claims

1. A paper comprising: a) a paper substrate and b) a preparation applied to the entire surface of at least one side of the paper substrate and containing at least one surfactant and at least one pigment with a particle diameter of 1 to 500 nm, but no binder, the preparation being a binder in a ratio to pigment of a maximum of 5 parts by weight of binder: 100 parts by weight of pigment (in each case based on the solids content).

2. The paper according to claim 1, characterized in that the preparation has an application weight of 0.5 to 20 g / m ² (atro) per side.

3. The paper according to claim 1 or 2, characterized in that the preparation contains 0.05 to 2.5 g / m ² (atro) surfactant per side.

4. The paper according to any one of the preceding claims, characterized in that the surfactant is an anionic, cationic, nonionic or amphoteric surfactant.

5. The paper according to one of claims 1 to 4, characterized in that the preparation contains 0.45 to 17.5 g / m ² (atro) pigment per page.

6. The paper according to any one of claims 1 to 5, characterized in that the pigment has a total cationic and / or anionic and / or nonionic charge.

7. The paper according to any one of claims 1 to 6, characterized in that the pigment is an oxide and / or mixed oxide of a metal and / or an oxide and / or mixed oxide of a semimetal / semiconductor.

8. The paper according to one of the preceding claims, characterized in that the preparation contains at least one further additive.

9. The paper according to one of claims 1 to 8, characterized in that the paper substrate contains at least one filler.

5 10. The paper according to claim 9, characterized in that the filler has a void volume.

11. The paper according to claim 9 or 10, characterized in that the filler has an oil number measured according to DIN EN ISO 787-5 of 10 to 150 g / 100 g filler.

ιo 12. The paper according to any one of claims 9 to 11, characterized in that the filler is selected from the group consisting of chalk, precipitated chalk, clay, talc, calcined clay, aluminum oxide, aluminum hydroxide, plaster, aluminum oxide hydrate, silicon dioxide, Silica, diatomaceous earth, titanium dioxide and mixtures thereof.

15 13. The paper according to one of claims to 12, characterized in that the paper substrate contains at least one additive.

14. The paper according to one of the preceding claims, characterized in that on the side of the paper substrate on which the preparation is applied, at least one further coating is provided on the preparation.

20 is there.

15. The paper according to claim 14, characterized in that the coating contains at least one pigment and at least one binder.

16. The paper according to claim 15, characterized in that the pigment has a particle diameter of 1 to 500 nm and is preferably selected from the group consisting of oxide and / or mixed oxide of a metal, oxide and / or mixed oxide of a semimetal / semiconductor and mixtures of the same.

17. The paper according to any one of claims 14 to 16, characterized in that the coating contains at least one further additive.

18. A method for producing a paper comprising the step: applying a preparation comprising at least one surfactant ιo and at least one pigment with a particle diameter of 1 to 500 nm to at least one side of a paper substrate, the preparation containing binders in a ratio to pigment of at most 5 parts by weight of binder: contains 100 parts by weight of pigment (in each case based on the solids content).

19. A method for producing a paper according to claim 18, characterized in that at least one further coating is applied to the side of the paper substrate on which the preparation was applied.

20. Use of the paper according to one of claims 1 to 17 in one

20 printing processes as substrates.

21. Use of the paper according to claim 20, characterized in that the printing process is selected from the printing process consisting of offset printing, digital printing, inkjet printing, gravure printing, flexographic printing, newspaper printing, letterpress printing, letterpress printing, sublimation printing, laser printing, electrophotographic

25 printing process and combinations of printing processes.